Interim solution method for dust control on saline dry lakebeds using minimal water resources

ABSTRACT

A method for controlling dust on a saline dry lakebed or similar environment enriched with sodium carbonate and sodium sulfate is disclosed comprising, the Interim Solution method that achieves resistance to windborne dust release. The Interim Solution is a dilute aqueous solution containing a divalent cation chloride salt and anionic polyacrylamide that can be applied to dust-emission prone lakebed surfaces by spraying or other means that achieves a relatively even application. The chemical reaction that occurs upon contact of the Interim Solution with the salts of the lakebed soil creates stable compounds that are interconnected by the long-chain molecules of the polyacrylamide that binds the molecules derived by the chemical reaction into a surface skin that protects against wind erosion. A salt byproduct, sodium chloride, remains soluble in the near surface soil will tend to seal the surface against evaporation.

This patent application is a continuation-in-part of acontinuation-in-part application Ser. No. 13/157,240 filed Jun. 9, 2011that was a continuation-in-part of non-provisional patent applicationSer. No. 12/841,971, filed on Jul. 22, 2010, that claimed priority to:U.S. Provisional Patent Application Ser. Nos. 61/228,271 entitled“System and Method for Use of Natural Brine To Prevent Fugitive DustUsing Minimal Water,” filed on Jul. 24, 2009; U.S. Provisional PatentApplication Ser. No. 61/254,112 entitled “System and Method for Use ofNatural Brine to Prevent Fugitive Dust Using Minimal Water,” filed onOct. 22, 2009; U.S. Provisional Patent Application Ser. No. 61/315,461entitled “Method for Employing Clay for Construction of Low Cost PondLiners,” filed on Mar. 19, 2010; U.S. Provisional Patent ApplicationSer. No. 61/326,468 entitled “Chloride Salts With Divalent CationsProvide Temporary Surface Stabilization in Saline Systems Dominated bySodium,” filed on Apr. 21, 2010; and U.S. Provisional Patent ApplicationSer. No. 61/358,249 entitled “Chloride Salts with Divalent Cations andPolyacrylamide Provide Temporary Surface Stabilization in Saline SystemsDominated by Sodium,” filed on Jun. 24, 2010.

This continuation-in-part non-provisional patent application also claimsthe benefit of the priority continuation-in-part application Ser. No.13/157,240 filed Jun. 9, 2011 that claimed the benefit of the priorityof continuation-in-part of non-provisional patent application Ser. No.12/841,971 filed on Jul. 22, 2010 that claimed the benefit of thepriority of U.S. Provisional Patent Application Ser. Nos. 61/228,271entitled “System and Method for Use of Natural Brine To Prevent FugitiveDust Using Minimal Water,” filed on Jul. 24, 2009; U.S. ProvisionalPatent Application Ser. No. 61/254,112 entitled “System and Method forUse of Natural Brine to Prevent Fugitive Dust Using Minimal Water,”filed on Oct. 22, 2009; U.S. Provisional Patent Application Ser. No.61/326,468 entitled “Chloride Salts With Divalent Cations ProvideTemporary Surface Stabilization in Saline Systems Dominated by Sodium,”Filed on Apr. 21, 2010; and U.S. Provisional Patent Application Ser. No.61/358,249 entitled “Chloride Salts with Divalent Cations andPolyacrylamide Provide Temporary Surface Stabilization in Saline SystemsDominated by Sodium.” filed on Jun. 24, 2010. The entire content ofnon-provisional patent application Ser. No. 12/841,971 andnon-provisional continuation-in-part patent application Ser. No.13/157,240 filed Jun. 9, 2011, both identified above, and theabove-identified provisional patent applications for which priority isclaimed for this non-provisional continuation-in-part application areincorporated by reference into this non-provisional continuation-in-partapplication to provide continuity of disclosure.

BACKGROUND AND SUMMARY

The present invention relates generally to the field of ecologicalmanagement and more particularly to the field of dust control orabatement of saline soils dominated by sodium salts using minimal waterresources. One embodiment of the invention was developed for the bed ofOwens Lake in Eastern California (FIG. 1) that is dominated by carbonateand sulfate salts of sodium: however, the embodiment described herein isapplicable to any environment that presents salt chemistry similar tothat within the Owens Lake bed, including for example, other saline drylakes or sumps receiving and concentrating water from agriculturaldrainage.

Soils enriched with sodium carbonate and sodium sulfate throughagricultural drainage, similar salty beds exposed due toanthropomorphically-changed hydrology (like the Owens Lake), and naturaldry lakebeds with shallow groundwater connection are prone to createlarge sources of airborne dust that can cause health and safety hazardswithin the surrounding region. An example of a natural system, OwensLake, was the historic terminus of the Owens River that was diverted forexport by the City of Los Angeles resulting in desiccation of the lakeearly in the last century.

The Owens Lake bed is highly saline with some locations containing up toaround 60% by weight of the salts sodium carbonate, sodium bicarbonateand sodium sulfate. When these salts are dissolved by rain or snowduring cold temperatures, they re-precipitate as decahydrate thatincorporates 10 molecules of water for each salt molecule. Thetemperatures governing re-precipitation that incorporates decahydrateoccurs at about 50 degrees Fahrenheit for sodium carbonate salts andabout 65 degrees Fahrenheit for sodium sulfate salts; these temperaturesmay vary based on the presence of other salts.

Re-precipitation of salts in the decahydrate form causes crystals toswell 4-5 times their volume. Decahydrate salt crystals lose watermolecules in alternating warm and cold temperatures in winter andespecially during warm sunny days. This process destroys soil cohesionand renders the surface easily lofted by only moderate winds of about 15miles per hour. This salt-phase-change mechanism is largely responsiblefor the severe dust problems at Owens Lake, prompting it to berecognized as the largest single dust source in the United States.

Federal and state laws mandate that the City of Los Angeles Departmentof Water and Power (LADWP) perform dust control for Owens Lake. Throughseveral decades of intensive study, three dust control methods have beenidentified by the agency responsible for monitoring and enforcing dustcontrol: wetting the surface, covering the surface with vegetation, orcovering the surface with gravel. Of these three, only surface wettingin constructed artificial (man-made) wetting basins has been able toaccomplish dust control within the time and scale required.

Unfortunately, wetting of the Owens Lake surface uses enormous amountsof water—LADWP has used four feet per year to plan for the requiredwater application for dust control through the dust control season. Thetotal amount of water use can greatly exceed 100,000 acre feet per yearon over 40 square miles of the lakebed—this amount is sufficient waterto supply about 400,000 families. Within the critically water-shortsemi-arid southeastern California region, this annual consumption ofwater for dust control is not sustainable.

During the process of desiccation, naturally saline Owens Lake waterconcentrated to form an evaporite deposit on the lakebed's lowesttopography. The evaporite deposit covers about 34 square miles, has anaverage depth of about 2.6 feet and varies in thickness from a fewinches to about 9 feet (FIG. 2). The evaporite deposit consists ofprecipitated salts and salt held in concentrated aqueous solution. Thisaqueous solution is brine, dominated by sodium chloride that remains insolution because it is much more soluble than sodium sulfate and sodiumcarbonate in common ambient temperatures at the Owens Lake. The sodiumchloride-rich brine isolates the potentially emissive salts of sodiumcarbonate and sodium sulfate from atmospheric desiccation, therebyprotecting the source deposit from being dust emissive. The term“wetting basin” is synonymous with “dust control wetting basin” and is apolygonal area enclosed by berms flooded with water to control dustemissions from the lakebed as seen in FIG. 2.

The present invention includes systems and methods that protect thesurface from releasing dust, consuming minimal water resources forstartup, and thereafter consuming little or no additional water formaintenance while using, the present infrastructure that was built toprovide surface wetting with only minor modification. Each of threemethods provides the surface protection by working with the naturalproperties of the salts present within the Owens Lake system. In one ofthe methods a different type of salt is imported that, with anotheringredient, works to stabilize the surface.

The three methods that have been identified for conserving water duringdust control are described as bullet points (1), (2) and (3), below. Theembodiment of the present invention comprises the third bullet point.

-   -   (1) The use of brine from salt mined, dissolved and moved from a        natural source deposit to create salt deposits within        reconfigured wetting basins, including basins that were        originally created for dust control using fresh water flooding.        These created salt deposits will form a “Brine Membrane” that        mimics the stable non-dust-emissive source deposit by having        horizontal beds of precipitated salts with the most soluble        salts retained within a sodium chloride brine solution that        bathes and caps the precipitated horizontal beds of salt        beneath. The control of evaporation by the Brine Membrane        maintains the deposit in a wetted state (non-desiccated,        non-dust emissive).    -   (2) The use of measurements of soil temperatures to predict when        the soil temperature within flooded wetting basins reaches and        exceeds the temperature when the salts of sodium sulfate and        carbonate will no longer undergo phase changes that would render        a desiccating surface prone to windborne dust emission. This        method is called “Springtime Conservation” because it curtails        superfluous additional water for dust control in wetting basins        as the temperatures warm during the spring.    -   (3) The use of small quantities of polymer and divalent cation        salts of chloride (for example calcium chloride) to stabilize        emissive areas of exposed lakebed, not yet treated by        construction and flooding of wetting basins. This is called the        “Interim Solution” since it allows for later conversion to a        wetting basin or to conversion by the Brine Membrane method once        the wetting basin is constructed. The Interim Solution can        provide stability on very large areas and can provide protection        for wetting basins that were formerly filled with fresh water        for dust control.

All three of these methods provide a transformation from the currentwasteful practice of flooding emissive surfaces with large amounts ofwater that evaporates annually, while protecting the lakebed surfacefrom windborne dust emission. A brief description of the three methodsfollows. The embodiment of the present invention, Interim Solution, islisted third.

Brine Membrane

The Brine Membrane method of the embodiment may be summarized asrequiring mining, dissolution and movement of large quantities of saltsfrom a source deposit to prepared wetting basins where it will formsimilar salt deposits that will replace fresh water, transforming thewetting basins from a wasteful byproduct of evaporation to a non-waterconsuming, non-dust emissive surface. Sodium chloride, the salt thatprovides the protective mechanism responsible for retaining thenon-emissive qualities of the lakebed source deposit, may be present inlimited but sufficient quantities, if managed correctly. Thus, managingthe sodium chloride resource between the salt beds created within thewetting basins and the source deposit ensures that this mineral is notdepleted in either environment so that both are protected fromdesiccation so that the salt masses remain non-dust-emissive. Becausethe salt bed that is created tends to remain wetted perpetually, theBrine Membrane method qualifies as shallow flooding that is recognizedby the regulatory agency as a Best Available Control Measure, approvedfor application to control dust from the Owens Lake bed.

The Brine Membrane concept arose out of scientific discoveries at OwensLake during study of evaporation from the evaporite deposit as reportedby the inventor and others in an article entitled “Floating brinecrusts, reduction of evaporation and possible replacement of fresh waterto control dust from Owens Lake bed, California,” Groeneveld, D. P.,Huntington, J. L. and Barz, D. D., Journal of Hyvdrology, 392 (2010)211-218, published Oct. 15, 2010. The following two paragraphs are thesummary and conclusion from that paper.

“Owens Lake, California, a saline terminal lake desiccated afterdiversion of its water source, was formerly the single largestanthropogenic source of fugitive dust in North America. Over 100 billionm³·yr⁻¹ of fresh water are projected to be used for mandated dustcontrol in over 100 km² of constructed basins required to be wetted tocurtail emissions. An extensive evaporite deposit is located at thelake's topographic low and adjacent to the dust control basins. Becausethis deposit is non dust emissive, it was investigated as a potentialreplacement for the fresh water used in dust control. The depositconsists of precipitated layers of sodium carbonate and sulfate bathedby, and covered with brine dominated by sodium chloride perenniallycovered with floating salt crust. Evaporation (E) rates through thiscrust were measured using a static chamber during the period of highestevaporative demand, late June and early July, 2009. Annualized total Efrom these measurements was significantly below average annualprecipitation, thus ensuring that such salt deposits naturally remainwet throughout the year, despite the arid climate. Because it remainswetted, the evaporite deposit has the potential to replace fresh waterto achieve dust control at near zero water use.

Floating salt crusts that cover sodium chloride-dominated brine are theexpected surface condition for the natural evaporite deposit at OwensLake. These floating crusts reduce evaporation to levels less thanprecipitation, thus ensuring that the evaporite body remains wetted atall times. Moving salts from an existing evaporite deposit to the dustcontrol basins may, therefore, offer a viable replacement for the freshwater used for dust control on the dry lakebed. Using the adjacentnon-dust-emissive natural evaporite deposit as a model, salt depositscreated in the dust control basins could be engineered to containsubstantially equal proportions of precipitated salts of sodium sulfateand sodium carbonate, below, capped by a layer of sodiumchloride-dominated brine. Salt crusts would form atop this supernatantbrine layer to reduce annual E to less than annual precipitation, thusensuring that the engineered salt deposits would also remain wet andnon-emissive. Once established, the natural properties of salt depositsmodeled upon the natural deposit may enable complete dust control withnear zero additional fresh water.

These scientific findings prompted additional research that concludedthat creation of the Brine Membrane over large areas of the Owens Lakebed would introduce profound water conservation for dust control. Thisresearch also found that large-scale application of the Brine Membraneis practical because there are sufficient salts within the evaporitedeposit to treat a large proportion of the existing dust control wettingbasins without creating additional fugitive dust sources, and that thetechnology required can be adopted for Brine Membrane implementation.The Brine Membrane effectively transforms surfaces of the Owens Lakebedinto stable non-emissive salt beds using a minimum of water resources.

Another scientific finding concerning the Brine Membrane was that theproperties of the sodium chloride-dominated brine are what enable thecrusting to float atop the brine. The density of the brine solution isincreased because it includes dissolved ions of carbonate and sulfatepermitting the sodium chloride crust to float atop the brine. Thefloating crusts of sodium chloride are what reduce evaporation. Withoutthe density enhancement by carbonate and sulfate ions, for example inpure solutions of sodium chloride, these crusts will form but notperpetually float on top of pure solutions of sodium chloride.

Springtime Conservation

There are conditions that may obviate the conversion of an existingwetting basin by the Brine Membrane method—for example where the wettingbasin may serve an alternative function as a wildlife habitat or wherethe potential rate of percolation brine loss from the basin would beunacceptably high and the application of fresh water for dust controlmust be continued. Under these conditions, Springtime Conservationprovides a third water conserving embodiment of the method of thepresent invention. Springtime Conservation can potentially conservewater by safely curtailing supplies of water to wetting basins duringthe last two months of the dust season in May and June coinciding withintensive evaporation.

Current regulations that set forth the dust season at Owens Lake arebased upon observations of the annual period that dust is typicallyreleased, and requires that water be supplied to the wetting basinsthrough this period, each year until the end of June. Rainfall duringthe warmer seasons is known to create competent “summer crusts” thatremain until the surface either becomes physically damaged by wind orother mechanical disturbance or undergoes wetting during the winterfollowed by salt phase-induced destruction of soil cohesion as describedabove. The summer crust occurs because salt precipitation occurs abovethe threshold temperatures described in paragraph 005. The Junethreshold arose because summertime winds are generally insufficient tocause dust emission from those portions of the Owens Lake bed thatemitted dust during the winter and spring despite conditions of thesurface conducive to dust release. The key to re-stabilizing emissiveportions of the lakebed each summer is to create a summer crustfollowing rainfall during warm weather. Such rewetting and crustformation typically occur each year because at least some rainfalloccurs during the warmer months.

The creation of a summer crust protects lakebed surfaces from dustemissions until a wetting basin is again flooded for dust control inlate summer in preparation for the new dust season. The point-in-timewhen water supplies to wetting basins can be safely curtailed eachspring is defined by soil temperatures that govern the phase changes ofsodium sulfate and sodium carbonate salts. If soil temperatures aresufficiently warm, above about 50 degrees Fahrenheit for sodiumcarbonate and above about 65 degrees Fahrenheit for sodium sulfate, andif sufficient salts are present, as indicated by brackish water withineach wetting basin, the formation of a summer crust will occur. Summercrusts are stable because the salts precipitate with few inclusive watermolecules in the crystalline matrix thereby forming a bridge forgrain-to-grain contact within the soil. When dry, summer crust isextremely hard and durable.

Springtime Conservation is a method embodiment that curtails waterdelivery to the wetting basin when temperatures are safely forecasted toinduce summer crust formation. This method, favored for wetting basinsthat are undesirable for conversion to Brine Membrane, for example,serving wildlife habitat values or having high rates of seepage loss,can still save almost one third of the water that is used within suchwetting basins. Springtime Conservation transforms the dust controlwetting basins in the last two months of the dust season from a highlyevaporative wetted surface that requires constant resupply with waterinto a dry non-emissive surface, thereby conserving significant waterresources.

Interim Solution

In conditions where the lakebed surface has been identified as emissivebut where wetting basins have not yet been created, a third embodimentof the invention called the Interim Solution can be implemented; thisembodiment of the method utilizes a mixed solution comprisingpolyacrylamide (PAM) and calcium chloride or other divalent cationchloride salt. When applied onto the lakebed surface, the cation, forexample calcium, creates precipitates with the sulfate and carbonateions that will remain stable in a high pH lakebed environment (as gypsumand lime). Small quantities of PAM serve to tack these precipitatestogether electrochemically creating a surface skin that is resistant towind erosion and weather-induced deterioration that is effective for oneor more “dust seasons”—the dust season has been defined for the OwensLake by air quality regulators as the period between October 1 and June30 of each year. Although the Interim Solution is anticipated to betemporary, it is comparatively inexpensive, and can be reapplied asnecessary. The Interim Solution transforms a surface that gives rise tofugitive dust to a stable non-emissive surface using minimal waterresources.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 comprises three maps to illustrate the location of Owens Lake inCalifornia in the United States;

FIG. 2 is a Landsat TM satellite view of Owens Lake, modified by theinventor with a dashed line to show the approximate location of theevaporite deposit and surrounded by dust-control wetting basins (darkpolygons), taken in late Spring, 2009;

FIG. 3 is a flowchart depicting an overview of the system to place theembodiments in context with respect to the three methods for dustcontrol using minimal water resources;

FIG. 4 is a flowchart of an embodiment depicting a method in accordancewith one aspect of the present invention, a Brine Membrane, that is astable, non-dust-emissive salt bed with annual evaporation rates lessthan annual rainfall;

FIG. 5 is a schematic cross-sectional view of a lakebed illustrating thewater savings attributable to aspects of the present invention;

FIG. 6 is a graph showing temperature-dependent single salt solubilityfor the dominant salts in the Owens Lake as a guideline for managingwater temperature required to dissolve the major salt species mined fromthe source deposit for establishing the Brine Membrane within thedust-control wetting basins;

FIG. 7 is a flowchart of an embodiment depicting a method in accordancewith another aspect of the present invention, the Interim Solution, thatis a temporary application to stabilize dust-emissive surfaces usingsalt and polymer chemistry;

FIG. 8 is a flowchart of an embodiment depicting a method in accordancewith still another aspect of the present invention, SpringtimeConservation, that uses measurements of soil temperature to decide whento curtail water supply to wetting basins in the spring; and

FIG. 9 is a graph showing the results from multiple penetrometer testsof the force needed to break the crust formed after treatment by threeformulations of the Interim Solution. All three of the treatmentsinduced surface protection against the effects of wind erosion bycreating a surface skin resistant to the erosive force of wind. Thetreatment with 6 mm application of 1:30 dilution of calcium chlorideplus two grams of PAM offered the best surface protection.

DETAILED DESCRIPTION

As will be appreciated by those skilled in the art, aspects of thepresent invention are described in detail with reference to severalembodiments of methods that transform dust-emissive portions of salinesoils dominated by sodium salts, such as a dry lakebed, including, butnot limited to, the Owens Lake bed surface, to provide complete dustcontrol while minimizing water use. Descriptions and figures areprovided to place the present invention, The Interim Solution, intocontext within the suite of three potential water conserving dustcontrol treatments that are identified here.

Method for Selection of Optional Dust Control Methods

As shown in FIG. 3, a method of dust control in accordance with oneembodiment can begin at START (S100). At step S102 it is determinedwhether or not there are dust emissions from a discrete region or site,such as a dry lakebed, by monitoring air quality at step S104. As usedherein, the term “dust” includes any particulate matter that is expelledor can arise from the earth surface into the atmosphere by natural windsor by wind artificially and inadvertently caused by vehicle passage onthe earth surface where it can be inhaled by humans or other animals.

In the event that there is no prevailing dust emission, then the methodof the preferred embodiment returns to air quality monitoring step S104awaiting potential future dust emission. Those of skill in the art willappreciate that implementation of the embodiment of methods describedherein will likely result in mitigation of identified dust emissions,but that all surfaces of concern, whether subject to control, or not,should be continuously monitored for any deterioration resulting in dustemission that violates standards. Step 104 is the responsibility of theagency that monitors and enforces air quality of a lakebed or othersimilar environment.

Step S106 of the method embodiment queries whether there is an existingdust control wetting basin at the site for dust control. If the responseis affirmative, then the method proceeds to S108 that queries whetherthe wetting basin could be converted to Brine Membrane. The decision atS108 is made in consideration of whether (1) seepage losses are high andtherefore potentially problematic for retention of the bathing sodiumchloride brine for the Brine Membrane method that would protect the saltbed mass from desiccation, (2) it is desirable to convert the wettingbasin to Brine Membrane control, but such control must be postponed dueto priorities and resources, (3) there are competing uses for thewetting basin such as a wildlife habitat that would render the BrineMembrane method less desirable, (4) the location of the wetting basinproximal to infrastructure and the source deposit of salt that wouldenable an economically viable conversion to Brine Membrane, (5) theBrine Membrane is less economically viable than treating and retreatingthe surface using the Interim Solution method or (6) conversion to BrineMembrane is limited by the decision of the regulatory agencies or Stateof California, the owner of much of the affected portions of the OwensLake bed. The level of seepage loss can be judged to be too great forforming a Brine Membrane if the loss of brine occurs within severalyears and with comparison to the cost of implementing other dust controlmeasures and in consideration of the longevity of such other measures.Making these determinations can be readily performed by one of ordinaryskill in the art.

If the response to query S108, whether to convert an existing wettingbasin to Brine Membrane is affirmative, then the method of theembodiment proceeds to step S120 which refers to FIG. 4, a continueddescription of the embodiment, described in detail below.

If the response to query S108 is negative for any reason, then themethod of the embodiment proceeds to S114 that queries whether theexisting wetting basin can be treated to curtail and conservelate-season water delivery using the Springtime Conservation method. Ananswer in the affirmative passes the process to step S170 of FIG. 8 thatdescribes Springtime Conservation. A negative reply to S114 indicatesthat the wetting basin is being managed by some other criteria—aswildlife habitat, for example.

Returning to S108, and a no answer for whether the existing wettingbasin should be converted to Brine Membrane, an alternate pathway leadsto the query at S118 for determining whether wetting may be discontinuedfor water conservation. An answer in the affirmative leads to S150 thatinvokes using the Interim Solution. A no answer to query S118 leads toSpringtime Conservation. Hence, not converting an existing wetting basinto Brine Membrane leads to management to retain wetness (S116), use ofInterim Solution to stabilize the surface or to Springtime Conservation(S170).

Returning to decision block S106, if there is no existing wetting basin,then the method of the embodiment proceeds to step S110 that querieswhether a wetting basin should be created. Creation of a wetting basinshould be judged on one of the following criteria: (1) seepage lossrates sufficiently low to retain brine, (2) location sufficientlyproximal to enable economically viable conversion of the location to aBrine Membrane, (3) location especially suitable for wildlife habitat.If the response to S114 is negative, then the method proceeds to stepS150, referencing FIG. 7 and a continued description of the InterimSolution method, described in detail below.

Brine Membrane Method

FIG. 4 implements the decision made at step S108 to convert an existingwetting basin to Brine Membrane. The first step at S124 reconfigures theexisting wetting basin so that the basin requires a much lower volume ofsalt to create a stable bed than the volume of fresh water previouslyused to control dust. This reconfiguration is shown on FIG. 5 where anexisting wetting basin, indicated at 10, covering an area of lakebed 12,consists of an existing main berm 14 that encloses a depth of water whenthe wetting basin is filled to capacity 16 to protect the lakebed fromdust emissions. To reduce the volume necessary to file the wettingbasin, interior berms 18 are built that lower the depth required tocover the lakebed, producing much shallower depth than the originalwetting basin 20. Reconfiguring the wetting basins, thereby conservessalt and saves money, energy, time, and water in mining, transportingand establishing the Brine Membrane.

Step S140 of the method embodiment creates hot water to dissolve thesalts mined from the evaporite deposit as indicated in step S142. Hotwater can be generated through passive solar or other means and is anecessary step that will permit rapid dissolution of the salts,especially sodium carbonate and sodium sulfate whose solubilities arehighly temperature-dependent. In FIG. 6 single salt solubility for majorsalt species, indicate that the effective temperature to bring sodiumsulfate and sodium carbonate into solution should optimally be above 25degrees Celsius (77 degrees Fahrenheit), necessitating heating. Asindicated in FIG. 6, those skilled in the art will appreciate thatenclosing, piping or otherwise transporting brine solutions nearsaturation run the risk of massive precipitation if the temperaturedrops below the solubility point for these salts. Once plugged byprecipitated salts, such piping is generally a total loss. Hence, atFIG. 4, block S144 is a step that calls out dilution of the brine sothat it can be safely transported in consideration of the saltconcentration and lowest temperatures that will occur in the pipe orother conveying means of the brine to the wetting basin that can beoptimized empirically. The imported brine solution from block S144 canbe applied in step S126 to the wetting basin by means such as flooding,or other suitable means for dispersing liquid solutions upon a surface.

In another alternative to the method of the embodiment, sodium chloridemining and transport is managed so as to protect salt masses fromdesiccation and becoming sources of fugitive dust, either within thesource deposit or where created within the wetting basin. The method ofmanagement includes control of predetermined target ratios of the sodiumchloride salt to other salt ion species, including sodium carbonate,sodium bicarbonate and sodium sulfate, in a ratio that lessens thepotential for depletion of sodium chloride within the source deposit.One of ordinary skill in the art can determine such target ratios withinblocks S142 and S144, not specifically identified in FIG. 4.

In another variation of the method of the Brine Membrane embodiment atS126, the brine solution can be applied at the lowermost portion of thewetting basin in order to: (1) add the brine in a manner that willminimize the ratio of the surface area to the depth so as to slowoverall evaporation during filling, (2) reduce the potential for rillerosion of the lakebed substrate, and (3) help achieve better mixing ofthe salts such that the Brine Membrane method provides continuous,stable salt beds.

Following application of the brine solution to the wetting basin in stepS126, step S128 of the method allows evaporation, and consequentconcentration and precipitation of the salts from the brine solutioninto stable horizontal beds of sodium carbonate, sodium bicarbonate, andsodium sulfate capped by a protective layer of brine that is dominatedby sodium chloride, thereby creating the Brine Membrane. In thisoperation, sodium chloride will remain in solution because it is moresoluble over the range of ambient temperatures within the lakebed thanthe other common sodium-dominated salts as indicated in FIG. 6.

In step S130 of the method of the brine embodiment, a query is made asto whether the flooding of the wetting basin has produced the desiredstable condition of the Brine Membrane. If the response is affirmative,then the method of the embodiment proceeds via S132 to stepS104—continuous future monitoring. If the response is negative, then themethod proceeds to step S148 in which the wetting basin is refloodedwith water at a predetermined time that provides the correct ambienttemperatures for precipitation of sodium salts of carbonate, bicarbonateand sulfate as the resulting brine is concentrated by evaporation. Thismay happen, for example, during the autumn season when seasonal coolingwill create this condition. Additional salts may need to be added byimplementing step S148 to achieve the correct depth and/or mix of saltsin the wetting basin. Missing the desired stable endpoint by the BrineMembrane, production of stable wetted method in the horizontal beds ofprecipitate instead, can create an undesirable condition of spatialfractionation of salt species where potentially dust-emissive salts areexposed to the atmosphere. This can occur if the evaporation of thewater from the brine is high while the wetting basin is filling and ifthe brine is run across shallows with very high evaporation rates. Thisfactor can also be remedied at the time of brine entry by monitoring andincreasing the proportion of water within the brine. Also, filling thewetting basin at the downstream end will tend to prevent this conditionfrom occurring for reasons described above.

It is assumed that for Brine Membrane conversion, potential seepagelosses and static water table levels will have been measured andunsuitable portions of the lakebed with high seepage rates and/or deepwater tables will have been avoided. However, in the event that theseepage losses from the wetting basin cause the reduction of asignificant portion of sodium chloride-dominated brine that percolatesfrom the wetting basin, sodium chloride brine can be recharged directlyfrom solutions that develop atop the source deposit each winter due todirect precipitation and/or runoff onto the source deposit from regionaldrainage. This “borrowing” of additional sodium chloride-dominated brineis subject to understanding and managing the overall sodium chlorideresource in evaporite deposit. The same site infrastructure used for thesteps in FIG. 4 can be used to resupply the sodium chloride, mixed withother dominant salts, if desired, to maintain the brine membrane,thereby protecting the surface from dust emissions while committing onlya minute fraction of the fresh water formerly used for dust control. Oneof ordinary skill in the art can monitor, understand and manage thesystem-wide balance of sodium chloride to assemble sustainable harvestand export of the sodium chloride while protecting the source depositfrom desiccation (such monitoring and management is not specificallyidentified in the figures).

Springtime Conservation Method

Directing attention back to the flowchart in FIG. 3, in decision blockS108 after determining in step S106 that there is an existing wettingbasin wherein conversion to the Brine Membrane method is not acceptable,the method passes to step S114 querying whether the SpringtimeConservation method should be invoked. If no, then the management of thewetting basin is, therefore, following some criterion other than waterconservation, for example maintaining a wet condition for waterfowl. Ifthe answer to the query is yes, then the existing wetting basin can besubjected to analysis for Springtime Conservation, a method embodimentas described in FIG. 8, starting at step S172.

Step S174 determines, by testing, whether the wetting basin hassufficient salts present in the lakebed substrate to cause the waterreleased for dust control to become brackish-very salty, though not tothe extent of brine. Residual salts in the soil and the flooding waterare necessary for attainment of the desired end condition for SpringtimeConservation, a summer crust that is stabilized by salt crystals thatprovide grain-to-grain bridging that arms the soil against the action ofwind. In some sandy soils, particularly at the uppermost elevations ofthe wetting basin may have been leached, particularly if the soil issandy, and these soils will be less suitable for the SpringtimeConservation method without addition of native salts. One of ordinaryskill in the art can perform testing and determine whether salt contentsin the receiving wetting basin are sufficient for achieving a summercrust. A lakebed salinity of 3% or less by weight is generallyinsufficient for fostering the desired summer crust condition.

In the event that the answer to Step 174 is no, implying insufficientsalts to achieve a stable crust, the salts can be recharged to thewetting basin in block S178; the salt recharging adds the salts that aremined, dissolved and imported at Step 176 from brine mining andgeneration in steps S140, S142 and S144 on FIG. 3. In the event that thetest result in step S174 is yes, then the process passes to step S178comprising a test for the soil temperature within the wetting basin. Ifthe soil temperature is either at or above, or forecasted to be at orabove, the governing temperature for the phase change of the dominantsalts in step S180, the Springtime Conservation method is invoked atstep S182 and water delivery to the wetting basin is curtailed. Thegoverning temperature about 50 degrees Fahrenheit for sodium carbonateand about 65 degrees Fahrenheit for sodium sulfate—actual values varyingdue to the presence of other salts and as can be tested and understoodby a person having ordinary skill in the art. Curtailment of theunnecessary additional water of water that would be supplied until June30, thus saving about 32% of the water used for dust control through theentire October 15 to June 30 dust season.

In the event that curtailment is invoked, the final step in theSpringtime Conservation method embodiment passes back in block S184 tostep S104 of FIG. 3 that provides for monitoring of the system.

Interim Solution Method

Referring back to step S110 where an area of the lakebed was identifiedas dust-emissive, did not yet have a wetting basin, nor was planned toreceive a wetting basin, protecting the surface may be accomplished byusing the Interim Solution embodiment in FIG. 7, that starts at S152.This method may comprise application of a dilute aqueous solution,containing one or more divalent cation chloride salts, for example,readily-available salts of calcium chloride or magnesium chloride, and adissolved portion of an anionic polyacrylamide (PAM), that are mixedtogether to form a treatment solution. The treatment solution forcalcium chloride is prepared by diluting a saturated aqueous solution ofcalcium chloride by 15 to 45 times with fresh water and to dissolvingthe PAM at a rate of from one to three grams per liter of the dilutecalcium chloride solution. Other suitable salts and polymers can be usedin conjunction with or as substitutes for the divalent cation salts andPAM polymer noted herein.

At S154 testing determines the amount of salts in the surface to betreated, querying whether there is greater than 3 percent weight contentof the native salts of sodium carbonate and sulfate. An answer in theaffirmative will typically be the result since the lakebed is enrichedwith these two native salt species and the procedure then passes to stepS158 where the lakebed surface will be treated with the treatmentsolution. The treatment solution will dissolve the native salts in thelakebed and the divalent cations of, for example, calcium chloride willform stable precipitates of carbonate (limestone) and sulfate (gypsum).Sodium chloride is a byproduct of this reaction that remains in solutionwithin the soil matrix where it will tend to migrate to the treatedlakebed surface wetted by treatment solution application by capillarityand evaporation to form thin sodium chloride crusts that function toreduce evaporation. PAM functions to electrochemically tack theprecipitates and clays of the surface together, increasing surfacestability to resist the effects of wind and weather.

If, at block S154, the answer to the query for whether the surfacecontained greater than 3% by weight of the native salts is no, then themethod passes to block S156 that treats the surface with a pretreatmentsolution of dilute sodium carbonate and sodium sulfate salts rangingfrom 20% to 100% of saturation (saturation being determined bytemperature according to FIG. 6). The native salts of sodium carbonateand sulfate are present and minable from within the saline lake system,particularly from within the deposits shown in FIG. 1. The ionic contentof the pretreatment solution is unimportant as long as the total saltcontent is from 20 to 100% of saturation so that it enriches the nativelakebed to be stabilized with carbonate and sulfate ions.

The pretreatment solution is designed for substrates of the OwensLakebed that are dominated by coarse sands, particularly in the regionwhere the Owens River and other tributary inflows debouch onto thelakebed. Because these sands may have been leached by rain and snow overmany decades, they commonly contain lower concentrations of the dominantsalts of Owens Lake, sodium carbonate and sodium sulfate, and so, thetreatment solution, formulated to bond with dominant salts to stabilizethe soil, may not have sufficient concentration of these native salts tocreate the necessary stabilizing reaction. Any soil with concentrationsof sodium sulfate and carbonate salts less than a threshold of threepercent by weight require application of the pretreatment solution. Themajority of the Owens Lakebed is fine textured containing mostly silt-and clay-sized particles, and are highly enriched with sodium carbonateand sodium sulfate and so, should not require pretreatment forstabilization. After pretreatment, the method passes to block S158 inwhich the pretreated surface is then treated with the treatmentsolution.

Following application of the treatment solution, the treated surface istested to determine whether it has protected the surface from winderosion in step S159. Testing can be performed by two alternatives: amechanical device that directs a stream of air across the surfacemimicking natural high wind, or by penetrometry, wherein the resistanceof the surface skin created by the chemical reaction from the InterimSolution treatment of the lakebed is measured with a force gauge bypushing down and recording the force necessary to just penetrate thesurface. For one embodiment of the penetrometry option, the surface skinis tested in 36 separate spots within each site, before and aftertreatment, however, after treatment the surface is first allowed to dryprior to testing. The collected force data are then ranked as in FIG. 9from lowest to highest resistance. The degree of protection is judged bycomparing the forces required for penetration at the twelfth sample (theleast one-third of the total samples), counting up from the first andlowest ranked value. In this embodiment, a properly treated surface,when judged at the twelfth ranked sample, will have resistance topenetration at least double that of the native, untreated surface. Forlarge areas that have been treated, multiple sites may be chosen fortesting based upon appearance of the treated surface with representativetest sites chosen for each differing surface appearance.

The alternative protocol for testing using a directed stream of air mustfirst be calibrated to provide air flow over a test section with thesame effect as a wind of between 20 and 30 miles per hour with shear forthe flow impinging upon the test surface at an incident angle of lessthan 10 degrees. A surface is deemed sufficiently protected if noparticles are observed being released during this test and no erosion isevident upon the test surface.

If testing discloses that the surface is adequately protected, theembodiment of the method proceeds to step S160, that returns to stepS104 of FIG. 3 calling for continual monitoring of all lakebed surfacesto ensure that correct treatment has occurred and that dust is notreleased. If, however, if the answer to query S159 is no, the surface isnot properly protected, reapplication of the treatment solution may bemade. With each reapplication, the surface crusting will become moreresistant to wind erosion and remain intact for longer periods.

Though not required for the treatment solution to work, field tests haveshown enhancement for the stabilizing effects of the Interim Solutionmethod when the surface is compacted prior to application. At S156, aperson skilled in the art will recognize the dynamic nature of adust-emissive lakebed and the necessity to tailor the application rateand concentration of the treatment solution to the substrate to beststabilize the surface.

EXAMPLE EMBODIMENT

Other features and embodiments of the present invention are describedherein with reference to the particular site of Owens Lake, Calif. Thesystem and methods of the embodiments are adapted for use in dustcontrol wetting basins on the Owens Lake bed. The area of these basinswas 35.8 square miles measured on Apr. 22, 2011 by Landsat satellitedata used by regulatory agencies for monitoring wetting basincompliance.

The main goal of the Owens Lake embodiment is to control dust whileproviding nearly complete water conservation. Other goals are toimplement dust control for the lowest possible cost, as rapidly aspossible, and using a minimum of resources. For example, a method thatcompetes with the three conservation methods and that is under seriousconsideration, is the placement of four to eight inches of gravel atopengineering fabric—a method that may cost up to fifty million dollarsper square mile, and require burning millions of gallons of diesel fuel.Once gravel is in place it is permanent, allowing no other options.

By rough estimate the total dust control area under shallow flooding,plus areas that have been identified for conversion to active dustcontrol, and areas that are a likely future targets for dust control, isabout 46 square miles. As will be discussed below, of this area, 10 to20 square miles might be managed as wildlife habitat that will require awater supply irrespective of conservation. That leaves between 26 and 36square miles to be managed for dust control and water conservation usingthe Brine Membrane, Interim Solution and, and Springtime Conservationmethods.

The Brine Membrane is the most expensive of the three methods and mustbe limited in its application to those areas with low potential forpercolation loss of the sodium chloride dominated brine resource. Acursory evaluation of the Owens Lakebed indicates that there are about16 square miles of dust control wetting basins, existing and planned,that have both very shallow water tables and very slow percolationrates. The likely required time for full conversion to 16 square milesof Brine Membrane is around five years, a rate dependent upon the rateof mining and dissolution of brine. This time period allows for carefulmeasurement and management of salts on the lakebed.

There is great interest for management and enhancement of wildlifehabitat that has become established on the Owens Lakebed as a result ofthe many square miles of shallow flooding. The areas that have beendiscussed range between 10 and 20 square miles. Limited opportunityexists to conserve water within wildlife habitat through application ofSpringtime Conservation, though the potential extent of that applicationis not yet known. Especially for habitat that is seasonal and used bymigratory waterfowl, Springtime Conservation may have applicability forthe period after the waterfowl have departed, still well before therecognized end of the dust season (June 30, each year).

On a residual area of 10 to 20 square miles that cannot be treated byBrine Membrane or serve as wildlife habitat, dust can be controlledusing the Interim Solution. Operational application of the Interimsolution can take place by gradually taking wetting basins out ofservice allowing them to dry and treating them with this spray oncoating. The efficacy of the Interim Solution is determined by theresidual sulfate and carbonate salts of sodium that remain in thelakebed soil. These minerals attach to the calcium from the calciumchloride in the mix solution with PAM to form insoluble limestone andgypsum. Thus, in the event that fresh water has leached areas of thesenative salts required for Interim Solution to work, these salts can bereplaced by spraying, or by adding salts to the wetting basin inflowprior to conversion to be managed by the Interim Solution method. Thekey to a well-run management program employing Interim Solution will bean active effort to test conditions before treatment.

Within the Interim Solution PAM is weakly bonded electrochemically withthe calcium in the treatment solution, and when exposed to the salts inthe lakebed, creation of insoluble precipitates in the matrix of PAMmolecules provides an instant crust. Testing numerous formulations haveshown that highly dilute mix solutions (30× dilution of saturatedcalcium chloride) may actually work better than more concentratedformulas. Formulas may need to be varied according to the texture andsalt concentrations of the substrate that is treated.

Calcium chloride for the Interim Solution is mined approximately 200miles south of the Owens Lake and is available in sufficient quantitiesfor treatment of 10-20 square miles. Spray equipment developed foragriculture can be adapted to apply the Interim Solution. The largeareas for treatment do not need to be converted to Interim Solutioncontrol all at once and can best be gradually phased in over severalyears. The first areas to treat would be those identified to requiresome form of dust control but with none currently in place. After dustis controlled by the Interim Solution on such identified uncontrolledareas first, then this method can be applied to dust control wettingcells that are gradually decommissioned to no longer receive water.

Large areas of dust control can be accomplished using the InterimSolution method if it is employed in a “fire-brigade mode” where thetreatment is rapidly applied after the location is identified asemissive. Over time, some locations may receive repeated treatment.Retreatment is anticipated to create highly stable surfaces.Pre-treatment may be warranted for areas anticipated to be problematicbefore the dust season. Interim Solution can be applied any time of theyear, especially as a summer activity to ensure that all potentialdust-producing areas that have been identified during the previous dustseasons are treated and resistant.

Areas treated with Interim Solution must be made off-limits for anyvehicular traffic that would compromise the stabilizing crust. Likewise,once treated, the application equipment should be moved in such a manneras to stay off of the treated areas. Thus, a treatment with InterimSolution will terminate by withdrawal of the spray equipment treatingaccess ways as the last step so that no portions of the lakebed are leftwith broken crusts that are potentially emissive.

The regulatory agency for Owens Lake air quality maintains, and isimproving, a system of permanent, high resolution video cameras of thelakebed that are used for identification of dust producing areas. Thesecameras are operated daily and after dust has been detected, analysisprovides geocorrect maps of the dust sources that can be used to deployInterim Solution treatments within days of the event. Global positionsystem records of treated areas and identified areas will provideconfirmation of treatment as well as long-term electronic records forenhancing management.

A transition period of about five years is estimated to be required toachieve the 46 square miles of water-conserving dust control, if thisobjective is prosecuted intently. During transition to fullimplementation the wetting basins must remain flooded with fresh waterprior to conversion to Brine Membrane or Interim Solution.

The potential for using Springtime Conservation is especially greatduring the initial phase of a conservation program when the largestareas for dust control are using fresh water. After completion ofconversion to Brine Membrane and Interim Solution, the SpringtimeConservation method may still be of use, but only for that portion ofwildlife habitat where seasonal use has ended—for example, wheremigratory wildfowl have migrated on leaving the managed wetting basinbehind. Even though its useful life may be limited, SpringtimeConservation can be placed into service rapidly and save significantwater during the transition period.

The water that can be conserved with these methods is immense. For thehigh conservation assumption, with 10 square miles remaining flooded aswildlife habitat, the potential savings for treating the residual 36square miles with Brine Membrane or Interim Solution will eventuallysave over 92,000 acre feet of water per year (calculated using 4 feet ofseasonal water application over 36 square miles). For the low estimate,assuming 20 square miles as wildlife habitat, the conservation on 26square miles of the lakebed is over 66,000 acre feet per year.Additional savings through application of the Springtime Conservationmethod could potentially deliver additional water conservation afterconversion, and play a significant role in water conservation during thetransition to full application of Brine Membrane and Interim Solution.

Of the three methods, the Brine Membrane is the most complex since itwill require management of the evaporite source deposit as well as thewetting basin target deposits. The source of the salts used to createthe Brine Membrane within wetting basins in the first embodiment comesfrom the source evaporite deposit whose mineral content is shown belowin Table 1. These data resulted from over one thousand samplingboreholes made into the source deposit by three mining companiesoperating on Owens Lake over the past half century. The average brinephase content in the evaporite deposit is 30% by weight and the solidphase is 70% by weight. Abbreviations are Na, sodium; CO3, carbonate;HCO3, bicarbonate; Cl, chloride; SO4, sulfate.

TABLE 1 AVERAGE % WT. SOLID PHASE Na₂CO₃ 41.5 NaHCO₃ 25.0 NaCl 2.6Na₂SO₄ 12.4 Insoluble 9.1 H₂O 9.4 BRINE PHASE Na₂CO₃ 8.9 NaHCO₃ 0.2 NaCl18.0 Na₂SO₄ 4.5 H₂O 68.4

A sufficient quantity of salt exists within the source evaporite depositto supply all, or part of the existing approximately 36 square-milesurface of the wetting basins with salt deposits, while also maintainingin situ, sufficient salt in the existing evaporite deposit to protectthat surface from dust emissions. Following the methodology of the BrineMembrane embodiment ensures that salts from the source evaporite depositwould replace fresh water within the wetting basins in such a mannerthat the conditions created by the Brine Membrane in the Owens Lakewetting basins would maintain a stable non-emissive surface in the samemanner as the evaporite deposit.

The massive amount of salt required to be mined and moved to the wettingbasins for replacement of fresh water and the tendency for the limitedquantity of the sodium chloride ions to remain in solution requires thatexporting of the salts for creation of the Brine Membrane followsubstantially the same proportions of salts as in Table 1. This ensuresthat the sodium chloride is not depleted from the evaporite sourcedeposit. The protective crusting that controls evaporation is conferredby sodium chloride and this is important for both creating the BrineMembrane within wetting basins and for retaining such conditions withinthe mined and unmined portions of the evaporite deposit.

The Owens Lake climate, with three to four inches of rain and snowfalleach year is intensely arid and evaporation rates for fresh water exceedsix feet per year. Even so, the thin crusting that develops atop sodiumchloride dominated brine can reduce the annual evaporation rates tobelow the level of the annual total rain and snowfall received. Thespecial properties of the sodium chloride dominated brine in Owens Lakeenables support of a thin crust to remain floating atop the saturatedbrine beneath. The natural dissolution of small amounts of sodiumcarbonate and sodium sulfate in this sodium chloride dominated brinecauses an increase in the density of this liquid so that the crustremains floating. It can be demonstrated that such crusts can form onlytemporarily in surface tension but then sink through the liquid ofsaturated solutions of pure sodium chloride.

The property of the sodium chloride-dominated brine that reducesevaporation atop the Brine Membrane is what confers its effectiveness asa dust control measure—it allows rain and snow to enter and will remainwet, no matter how hot and dry the conditions. The regulatory agencyresponsible for measuring and enforcing air quality at Owens Lakerecognizes that, for purposes of dust control, the brine membrane is theequivalent of shallow flooding specifically because it retains the saltmass beneath in a hydrated state.

The principal salts of the Owens Lake are formed by cation sodium incombination with the anions of carbonate, sulfate and chloride. Sodiumsulfate and sodium carbonate change the hydration state due totemperature and water availability. To move the massive quantities ofsalts required in the Brine Membrane method across many square miles ofwetting basins, the source deposit may be mined mechanically. Because oftemperature-dependent solubility of both sodium carbonate and sodiumsulfate, the principal salt components within the source deposit,dissolving these salts will require heated water.

Passive solar collection is a convenient, potentially inexpensive andpractical method to generate sufficient hot water at the Owens Lakesite; however, other methods could be used to generate the hot water byburning fuel, especially during a cloudy day. Potential also exists forgenerating a certain amount of heated brine by flooding and drainingwetting basins, however, the insoluble fraction (Table 1) will tend toseal off the salt mass over time and this sealing must be overcome,perhaps through mechanical means such as scarification. Systems of dikedoff and mined parcels can be used to store brine of variable saltcontent that can be blended to create the desired mix to be exportedfrom the evaporite deposit. A number of mechanically mined parcelssupporting Brine Membrane conditions are currently located at the southend of the evaporite deposit. These parcels are highly stable againstwind erosion and can serve as the model to protect the evaporite depositonce it has been mined.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular terms “a,” “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising.” when used in this specification, specify thepresence of the stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below, if any, areintended to include any structure, material, or act for performing thefunction in combination with other claimed elements and specificallyclaimed. The description of the present invention has been presented forpurposes of illustration and description, but is not intended to beexhaustive or limited to the embodiments disclosed. Many modificationsand variations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the invention. Theexample embodiments were chosen and described in order to best explainthe principles of the invention and its practical applications, and toenable others of ordinary skill in the art to understand the inventionwith its various modifications as are suited to the particular usecontemplated.

What is claimed is:
 1. A method for temporary control of dust fromsaline dry lakebeds and similar environments that contain sodium saltsof carbonates and sulfates using a chemical reaction that creates a skinresistant to dust release comprising the steps of: determining if thedry lakebed contains sodium carbonate and sodium sulfate salts at levelsof 3% or more by weight that are sufficient to form a stable skin afterapplication of a treatment solution; if the dry lakebed contains saidlevel of sodium carbonate and sodium sulfate salts, mixing a diluteaqueous treatment solution containing at least one divalent cationchloride salt and an anionic polymer, spraying or otherwise spreadingsaid aqueous treatment solution on the dry lakebed, and if the drylakebed does not contain 3% or more by weight of sodium carbonate andsodium sulfate salts, additionally comprising the step of pretreatingthe lakebed surface by spraying, or otherwise evenly spreading apretreatment solution consisting of sodium carbonate and sodium sulfatesalts to bring the surface salt content of the soil to 3% or more byweight prior to application of the treatment solution.
 2. The method ofclaim 1 wherein said divalent cation chloride salt is selected from thegroup comprising calcium chloride and magnesium chloride.
 3. The methodof claim 1 wherein said anionic polymer is a polyacrylamide or similarcompound that weakly binds to the divalent cation in solution prior totreatment of the lakebed or other similar surface.
 4. The method ofclaim 1 wherein said polyacrylamide is dissolved into the treatmentsolution at a rate of from one to three grams per liter.
 5. The methodof claim 1 wherein said treatment solution contains calcium chloridediluted in the range of 15 to 45 times.
 6. The method of claim 1 whereinsaid treatment solution of calcium chloride is diluted in the range of20 to 40 times.
 7. The method of claim 1 wherein said aqueous solutionof calcium chloride is diluted by about 30 times.
 8. The method of claim4 wherein the rate of dissolving the PAM into the aqueous solution ofchloride is about 2 grams per liter.
 9. The method of claim 1 whereinapplication of the treatment solution results in an increase inresistance to penetration that is double that of the native untreatedsurface when evaluated at the least one-third of the ranked penetrationforce data that developed through multiple measurements.
 10. The methodof claim 9 wherein treated surfaces that do not result in a resistanceto penetration of double the penetration resistance at the ranked leastone-third of the penetration force from multiple samples, undergoreapplication of the treatment solution.
 11. The method of claim 10wherein a surface that has been retreated by reapplication of thetreatment solution again receives testing and retreatment until thesurface is judged to be stable.
 12. The method of claim 1 whereinapplication of the treatment solution results in an increase inresistance to the erosive force of wind such that a flow of artificiallyproduced air that impinges upon the surface at an incident angle of lessthan 10% and a velocity of between 20 and 30 miles per hour does notresult in destruction of the resultant crust nor the release of dustparticles.
 13. The method of claim 1 wherein the diluted pretreatmentsolution is in the range of 20 to 100% of saturation for sodiumcarbonate and sodium sulfate salts, the relative mix of these saltspecies being unimportant.
 14. The method of claim 13 wherein the ioniccontent of the diluted pretreatment solution is at least 20%.
 15. Themethod of claim 1 wherein the step of pretreatment is applied to theportion of the dry lakebed having coarse sands.
 16. The method of claim15 wherein the coarse sands have a grain size of at least 0.5 mm.
 17. Amethod for temporary control of dust from saline dry lakebeds andsimilar environments that contain sodium salts of carbonates andsulfates using a chemical reaction that creates a skin resistant to dustrelease comprising the steps of: determining if the dry lakebed containssodium carbonate and sodium sulfate salts at levels of 3% or more byweight that will be sufficient to form a stable skin after applicationof the treatment solution; if the dry lakebed does not contain a levelof sodium carbonate and sodium sulfate salts at a level of at least 3%,apply a dilute sodium carbonate and sodium sulfate salts in apretreatment solution to bring the surface salt content of the soil to3% or more by weight; mixing a dilute aqueous treatment solutioncontaining at least one divalent cation chloride salt and an anionicpolymer, spraying or otherwise spreading said aqueous treatment solutionon the lakebed portions to be treated for dust control; testing thetreated surface to ensure that the surface skin thereby created isadequately protected against wind erosion through penetrometry and/or adirected flow of air that mimics the action of natural wind; determiningthat the treated lakebed surface is properly protected against theerosive action of wind by penetrometer measurements of multiple pointsthat show at least double the resistance to penetration of the treatedsurface over the penetration resistance of the untreated surface, testedin the same manner, when evaluated at the least one third of the rankedvalues for penetration force; alternatively, determining that thetreated lakebed surface is properly protected against the erosive actionof wind by directing an artificially created flow of air at an incidentangle of less than 10 degrees and at a velocity of 20 to 30 miles perhour and confirming that the surface is stable against this artificialwind and does not emit dust; and in the event that the treatment did notresult in a stable surface protected from wind erosion through the testmethods, re-treatment of the surface with either, or both, the aqueouspretreatment and treatment solutions.